Sieve the flour and salt into a bowl. Boil the lard and the water in a pan. When dissolved, pour into the centre of the flour while hot. Work all together until a smooth dough is obtained. Cut off a third of the dough and reserve for the lid. Work the remainder on a floured board, gradually moulding to form a bowl shape. (A cake tin can be used as a guide.) Put on a greased baking sheet and fill the centre with the diced pork, sage and seasoning. Roll out the reserved third for the lid, brush edges of the pie with beaten egg and seal on the lid. Use trimmings to form leaves for decoration. Make a hole in the top and brush the pie all over with the egg. Bake at 400°F, 200°C, gas mark 6 for thirty minutes, then reduce heat to 350°F, 180°C, gas mark 4 for a further one and a half hours. Make a jelly from the bones, water, onion and seasoning by boiling for about two hours. Strain, and add the dissolved gelatine. Allow to cool but not set. Pour enough into the hole in the lid when the pie is cool to fill it; leave to set before cutting.